COMPARISON OF CORROSION RESISTANCE OF ZINC CHROMATE PRIMER TO EPOXY PRIMER
MCDONNELL AIRCRAFT CORP ST LOUIS MO
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The need to apply epoxy finishing systems to stock primed with zinc chromate primer has made it necessary to determine if the corrosion resistance of this system is adequate. It is also desired to use only one coat of epoxy primer on stock not already primed with zinc chromate primer provided adequate corrosion resistance can be attained. Test assemblies were fabricated of 7178-T6 non-clad aluminum panels. Panels covered with one coat of epoxy primer and panels covered with one coat of epoxy primer over one coat of zinc chromate primer were riveted to control panels covered with two coats of zinc chromate primer. The eight assemblies were exposed to salt spray corrosion tests. Assemblies were removed from the test environment at intervals of 168 hours, until all specimens had been removed. Examination revealed no corrosion on any of the test specimens after exposure to the salt spray environment for periods up to 672 hours. The single epoxy primer coat and the single epoxy primer coat over one coat of zinc chromate primer are considered equal in salt spray corrosion resistance.
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